Intel Skylake / Kaby Lake

Discussion in 'CPUs and Overclocking' started by Sweepr, Apr 16, 2015.

  1. DooKey

    DooKey Golden Member

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    What the heck is caring leader? None of these tech companies care one whit about any of us. I'm always confused by this kind of meme. Are people like you actually saying a company cares about you?
     
  2. formulav8

    formulav8 Diamond Member

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    gasme very strongly, Intel
    You get it then. Some person's ACT like a company care's about them. I've personally, never felt that way with any company caring for me. Some would probably defend Intel or AMD till their death it seems sometimes. Just IMO.
     
  3. MarkizSchnitzel

    MarkizSchnitzel Senior member

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    Well, depends on what you mean by "company".
    Accounting and investors sure as hell do not. They do want you to care for them, so they make the appearance of caring.

    On the other hand, to my eye, there are genuine enthusiasts like Miyamoto who do indeed care.

    i doubt though that can ever be the case in this sort of business :)
     
  4. SpoCk0nd0pe

    SpoCk0nd0pe Junior Member

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    Yes... but cutting the L3 cache size in half?
     
  5. LTC8K6

    LTC8K6 Lifer

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    But with 4X the L2 cache.

    Take your pick...
     
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  6. tamz_msc

    tamz_msc Golden Member

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    Everything has tradeoffs.
     
  7. dullard

    dullard Elite Member

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    • Intel 68xxK models were 1.5 MB of L2 cache and 15 MB of L3 cache. 16.5 MB total.
    • Intel 78xxX models are 6 MB (7800X) or 8 MB (7820X) of L2 cache and 11 MB of L3 cache. 17 MB or 19 MB total, depending on the chip. Assuming the rumored specifications are correct.
    The next generation has more total cache and a greater portion of that cache is faster L2. It is an improvement in the statistics that matter. I'm not sure that I would call that a problem. Nor would I say it is cutting L3 in half, since 11 is not half of 15. You might have wanted more and are thus disappointed. But the cache technically is much better.

    Lets look at the next step up:
    • Intel 6900K had 2 MB of L2 cache and 20 MB of L3 cache. 22 MB total.
    • vs.
    • Intel 7900X is rumored to have 10 MB of L2 and 13.75 MB of L3. 23.75 MB total.
    • Again, more total cache and the portion of faster L2 cache is much higher.
    Lets look at the next step up:
    • Intel 6950K had 2.5 MB of L2 cache and 25 MB of L3 cache. 27.5 MB total.
    • vs.
    • Intel 7920X is rumored to have 12 MB of L2 and 16.5 MB of L3. 28.5 MB total.
    • Again, more total cache and the portion of faster L2 cache is much higher
     
    #10507 dullard, May 15, 2017
    Last edited: May 15, 2017
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  8. tamz_msc

    tamz_msc Golden Member

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    All the corresponding parts have increased their core count by two. So total cache at a given number of cores has gone down.
     
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  9. dullard

    dullard Elite Member

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    That is like going from an i5 to an i3 and saying, hey there is less cache. While true, you are now comparing apples to oranges. You should compare one chip to the chip that is replacing it.
     
  10. DrMrLordX

    DrMrLordX Diamond Member

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    You have that a bit backwards. It's like we're going from an i3 to an i7.
     
  11. dullard

    dullard Elite Member

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    Going back to the start of this topic, it was about the 7820X. The 7820X has 19 MB of cache. It is replacing the 6850K with 16.5 MB of cache. The amount of cache increased.

    tamz_msc essentially wanted to compare the 78xx line to the 6900K chip just because the core count was the same. Call it i3 to i7 or i5 to i3 comparison, it doesn't matter. What matters is that he is comparing one category to a different category at a whole different price point.
     
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  12. tamz_msc

    tamz_msc Golden Member

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    You're essentially saying that the second digit of the name differentiates between some feature, while in reality it doesn't.
    Core for core, total cache has reduced, and the 8 core part has been relegated to 28 PCIe lanes.

    If you're directly comparing 6900K vs 7900X, then the increased cache is obviously due to the two extra cores. What's so special about that?
     
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  13. dullard

    dullard Elite Member

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    Um, the second digit is THE important feature in Intel's Core chips right now.

    Try going from a 7700 to a 7600. You lose hyperthreading and 2 MB of cache.
    Try going from a 7700 to a 7300. You lose two cores and 4 MB of cache.

    The second digit describes the features and price point. So you need to compare the second digit when comparing processors.
     
  14. frozentundra123456

    frozentundra123456 Diamond Member

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    No, I what one needs to look at is the cache per core. The cpu obviously doesn't know what chip it is replacing, the workload is split up among the cores and cache that are physically on the chip. That said, since the structure is different, I think trying to compare to older chips is pointless at this time. We will just have to wait for actual performance figures.
     
  15. tamz_msc

    tamz_msc Golden Member

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    No, those are more arbitrary when it comes to the HEDT.

    5930K vs 5820K - second digit differentiates between no. of PCIe lanes.
    6850K vs 6800K - now it's the third digit that does the same.

    Intel never laid out a naming scheme that allowed for consistently meaningful comparison.
     
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  16. DrMrLordX

    DrMrLordX Diamond Member

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    Why wouldn't he? Forget model numbers, just look at core count and cache sizes.

    Intel has reduced L3 to compensate for the increase L2 size and its effect on die size/transistor count. We don't know what will be the impact on performance.
     
  17. dullard

    dullard Elite Member

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    Because they aren't in the same target market. The price difference is almost double. Forget core count and look at prices.
     
  18. dullard

    dullard Elite Member

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    You are correct that the numbers are a bit more arbitrary when it comes to HEDT. But your PCI lane count thought only works on that one generation. For example, the 4930K and the 4820K both have 40 PCI lanes. Neither the second nor the third digit is a useful rule for the number of PCI lanes in HEDT chips.

    http://ark.intel.com/products/77780/Intel-Core-i7-4930K-Processor-12M-Cache-up-to-3_90-GHz
    https://ark.intel.com/products/77781/Intel-Core-i7-4820K-Processor-10M-Cache-up-to-3_90-GHz.

    What Intel has done though is differentiate on price. The higher the number (within a generation), the more features and the more the price. For HEDT, Intel has always had a chip near $1000, one near $600, one near $300 to $400. And recently they have a chip near $1700.
     
  19. RichUK

    RichUK Lifer

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    You'd think increasing the L2 cache would be a good move, considering it's faster than L3 cache.

    Simplistically speaking.
     
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  20. Sweepr

    Sweepr Diamond Member

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    I have an eye on that Core i9-7820X. High-clocked 8C/16T goodness with Skylake+ IPC and 4-channel DDR4. Skylake-X is the spiritual successor to Bloomfield IMHO. :)

    Only 15 days till formal launch if the rumors are correct.
     
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  21. SpoCk0nd0pe

    SpoCk0nd0pe Junior Member

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    I really don't care how version numbers compare. What I do care about is that they have cut the amount of L3 cache per core in half (you can keep the 0.125 mb).
     
  22. DrMrLordX

    DrMrLordX Diamond Member

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    Um . . . no? I just want to know if more l2 will compensate for the loss of L3, that's all. If it doesn't then the expected increase in IPC may not emerge, giving Intel a small problem (which they will compensate for partially with advanced clockspeed vs Broadwell-E).
     
  23. pantsaregood

    pantsaregood Senior member

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    Initially, the answer appears to be "the larger L2 should easily compensate for the lack of L3 cache due to the considerably lower latency," but there's a bit more complexity.

    Unless Intel has significantly altered their cache model, the L3 cache is still inclusive. This means that everything that exists in L2 cache on a given core also has to exist in L3 cache - this means that for every 1 MB of L2 cache, there is only 1.375 MB of L3 cache. Compare this to Broadwell-E, which had 0.25 MB of L2, there existed 2.5 MB of L3 cache.

    This effectively means that 72.7% of Skylake-X's L3 cache could be used for mirroring L2 cache, where Broadwell-E only used 10% of its L3 for mirroring L2 cache.

    Does this mean cache will be slower? No. We need benchmarks.
     
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  24. shortylickens

    shortylickens No Lifer

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    Stop worrying about level 3 cache.
    Level 3 cache is no better than RAM. And you really dont need an extra megabyte of RAM.
     
  25. Topweasel

    Topweasel Diamond Member

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    So if I am reading this correctly the Skylake now only has lets use the 7920x model only has 16.5 MB of unique cache between the L2 and L3 and the 6950x has 25MB of unique cache? So the hope here would be that the extra speed on the L2 make up for losing about 10MB worth of extra data total which in theory would mean more wasted cycles on refreshing the cache from memory?